Method of expanding pressure welded passageway panels to precise volume



Oct. 28, 1958 P. R. STAPLES 2,357,660

METHOD OF EXPANDING PRESSURE WELDED PASSAGEWAY PANELS To PRECISE VOLUME Filed Dec. 9, 1955 IN VEN TOR.

BY MAW ATTORNEY PAUL R. STAPLES.

United States Patent METHOD OF EXPANDING PRESSURE WELDED PASSAGEWAY PANELS TO PRECISE VOLUME Paul R. Staples, Louisville, Ky., assignor to Reynolds Metals Company, Louisville, Ky., a corporation of Delaware Application December 9, 1955, Serial No. 552,196 3 Claims. (Cl. 29-157.?!)

This invention relates to a novel method of making roll bonded passageway panels.

The Long Patent, 2,662,273, proposes to make expanded passageway panels by roll bonding two foreshortened metal sheets, with a foreshortened stop-weld pattern of appropriate passageway-circuit design interposed between them, to form a relatively elongate unexpanded panel and then hydraulically expanding its unbonded portions outwardly into flattening contact with rigid flat-faced dies, which are spaced apart a distance precisely equal to the final overall thickness desired in the expanded panel.

In practicing the Long method, ithas heretofore been diflicult, if not impossible, to secure the same degree of elongation in each of a succession of panels. As a matter of fact, the panel length will vary from panel to panel with a corresponding variation in the length of the unexpended passageway circuit system. As a consequence, the overall volume of the expanded passageway system, thus produced, will vary from panel to panel which is objectionable particularly in evaporator structures.

The principal objects of this invention are: to provide a novel method of securing precision in the final volume of the passageway system in the expanded panel; and to provide a novel method of securing the final thickness desired in the expanded panel and yet vary the degree of outward expansion in a manner compensating accurately for variation in volume due to variations in length.

Another important object is to achieve the foregoing objectives quickly and inexpensively.

All of the more important objects of my invention can be achieved by introducing a measured or precise volume of liquid into the panel to expand its passageway system to a corresponding volume and its thickness to a value slightly in excess of the desired thickness and then, while holding that liquid in the system, die flattening the panel between opposed platens to the final precise thickness desired. Where a measured or precise quantity of liquid is used in the expansion operation, the volume of the resulting expanded passageways has to be of precisely the same order of magnitude. The expansion pressure employed need only be of the value required to force this precise volume of liquid into the panel. If the ensuing expansion proceeds againsta yieldable medium such as air or rubber, it will inherently cause the expanded passageway walls to assume a somewhat circular curvature while the cross sectional area of the passageways will vary from one point to another. However, by

die-flattening the panel while holding that liquid in the system, the panel can be reduced to the requisite flatness and thickness while the pressure condition, which is established during the flattening operation, will insure uniformity in the thickness of the panel and in the cross sectional area of the passageway system.

The practice of my invention is illustrated in the accompanying drawing wherein:

Figure l is a partly broken plan view of a roll bonded or pressure welded, unexpanded passageway panel;

panded passageway panel 1, having a fluid inlet 2 for its unbonded portions 3, is connected through line 4 to a suitable source 5 of liquid under pressure. The expansion may be accomplished with the panel 1 either extending in the open air or positioned between dies 6 and 7, each die having its panel engaging platen faced with a planar sheet of yieldable material such as rubber.

In accordance with my invention, a measured amount of liquid is used in order to obtain, in the expanded panel, a corresponding degree of expansion providing the precise volume of internal passageway space desired. In other words, the volume of the expansion liquid precisely equals the volume of passageway space desired except possibly for the relatively minute amount of gas normally entrained in the expansion liquid. But, the compressibility of the liquid, due to entrained gas, may be readily compensated although it normally will not introduce any significant error. Normally a pressure below the free rupture pressure of the panel will be sufiicient to force the requisite volume of liquid into a roll bonded aluminum panel of conventional composition. This pressure for a conventional aluminum panel will be of the order of 700 to 800 p. s. i.

In expanding the panel, either in air or against rubber, the expanded passageways 8 will assume the oval or circular approaching shape indicated in Figure 4.

The expanded panel is now disconnected from the expansion liquid pressure source 5. It is placed between flattening dies or platens 9 and 10 with its inlet opening 2 aligned between clamping members 11 and 12, which are resiliently mounted upon the dies 9 and 16 in opposed relationship. In disconnecting panel 1 from the fluid pressure source 5 and transferring it to the dies 9 and 10, it is not necessary to close the opening 2, since little or no liquid will leak from the panel.

However, before the expanded passageways 8 can be flattened, the opening 2 must be closed, and this is ac complished by the clamping members 11 and 12, which engage and close the opening 2 before any flattening pressure is exerted upon the panels. As flattening pres sure is exerted upon the panel, the clamping members 11 and 12 will exert suflicient force to hold the inlet opening 2 tightlyclosed.

Now, as flattening proceeds, each passageway 8 of the system loses volume in the direction of the thickness of the panel. This tends to and does increase the pressure of the liquid in the passageway. This increase in pressure acts to expand the passageways 8 in the only available direction, which is more .or less parallel to the fiattening faces of the die members 9 and It). The use of gauge blocks 14 is recommended to determine the precise degree of flattening and prevent either excess or deficient flattening. As a consequence of this operation, the passageways are flattened, as indicated at 15 in Figure 7,

and the liquid pressure within such passageways is increased very substantially, ranging well above the free rupture pressure of the panel. The extent of this increase is, of course, determined by the degree of flattening. For the degree of flattening, which is indicated in the drawing only in a general way, the increase should range anywhere from 2,000 to 4,000 p. s. i. Naturally the expansion forces should be relieved before the dies are opened. This may be done by opening the clamps 11 and 12 by means not shown. Of course, it may also be accomplished by eliminating the clamps 11 and 12 and maintaining the connection of the panel with line 4 or establishing an equivalent connection, and releasing the final pressure through such connection.

My invention may also be used in connection with the practice of the Long process wherein panels are expanded, with expansion pressures well above their free rupture pressures, into flattening contact with the flat faces of rigidly held dies. Thus, for example, an expansion pressure of 3,000 p. s. i. may be employed to open and expand the passageways of a panel outwardly into fiat face contact with dies which are spaced a distance either equal to or slightly greater than the overall thickness desired in the final expanded panel product and appropriately flattened after excess expansion. But, by using the same precise volume of expansion liquid in successive panels, each of them will be expanded precisely to the same internal volume.

Having described my invention, I claim:

1. A method of expanding a pressure welded passageway panel composed of a pair of metal sheets containing unbonded potential passageway portions, comprising: introducing a measured volume of liquid under pressure into the panel to expand the unbonded portions outwardly to a panel thickness in excess of a predetermined panel thickness; sealing a measured volume of liquid within said panel; and flattening all expanded unbonded portions of said sealed panel simultaneously between opposed platens to said predetermined panel thickness.

2. The method of claim 1 wherein: said liquid introduction step is performed with the liquid pressure below the free rupture pressure of said panel.

3. The method of claim 1 wherein: said flattening step is performed with the liquid pressure within said panel rising to a value above the free rupture pressure of said panel.

References Cited in the file of this patent UNITED STATES PATENTS 1,925,854 Squires Sept. 5, 1933 2,662,273 Long Dec. 15, 1953 2,690,002 Grenell Sept. 28, 1954 

